Got to measure some samples then since they look promising. As to why they state equal to or smaller than 0.6% at 1kHz in a short datasheet (the Sep 2017 one without graphs linked in Mouser that I read when I was searching) as well as they state the same in the spec headlines of the expanded one you linked here, I would not guess.

PPS capacitors are my first choice for RIAA networks and line-level. But I have made some bad experiences when soldering these caps (ECHU, SMD) by hand. They quickly began to melt and changed their capacitance. Now I use leaded Kemet SMR Series, available in 5% at Mouser.

We have measurements in an oscillator circuit.
They were -140dB whereas WIMA FKP2 was -160dB.
You can argue 10x worse. But -140dB is just fine for me.

They are, like all SMD film caps, fragile.
You need to lower iron temperature to 300°C and use fine (0.3mm) leaded solder.
Then temperature is not so high, and also not so much heat energy applied.
Desoldering requires 2 irons. And you need to discard afterwards.
But otherwise we used them a lot without problems.All JFET open-loop RIAA pre-amp

There's a layout bug to fix before you do some testing with signal. R6 must be moved between R5's left side and RN1's ground side, else you will get unity gain from IC2 instead of 10X. George called to ask why no gain from stage two and we debugged it over the phone.

I see it now. My bad, going from your (correct) schematic to my (Eagle's) schematic.

Funny enough, I was looking at my Eagle's schematic the other day when I was ordering the components and that part of it looked a bit odd, but I didn't pay much attention. It appears that I should have.